This invention relates to a telephone call-diverter system whereby an incoming telephone call is automatically transferred to a predetermined remote telephone station and, in particular, to an improved system wherein a DC connection is extended to the incoming telephone line only after the remote telephone station answers the transferred call; and wherein an audio frequency signal channel is extended to the incoming telephone line independent of the DC connection.
Telephone call-diverter systems are known wherein apparatus is provided to extend, or forward, an incoming telephone call received at one station to another, predetermined station. Generally, such systems are constructed of numerous electromechanical switching devices, such as relays, solenoids, and the like. It has been found that such electromechanical switching devices exhibit rather limited operating characteristics and often must be replaced or repaired. Hence, such call-diverter systems are subject to frequent maintenence and repair schedules. This, of course, significantly limits the reliability of such systems. Also, with the advent of modern, high-speed telephone switching networks, the electromechanical switching devices admit of operating speeds which are often too slow in comparison with the electronic switching speeds of the telephone networks. This is capable of contributing to erroneous operation of such call-diverter devices.
In other prior art call-diverter systems, the sequence of operations therein are often dependent upon the conditions of the incoming and outgoing telephone lines. For example, operation of the call-diverter is usually initiated in response to an incoming ringing signal. Such call-diverters exhibit the capability of automatically transmitting dialing signals over the outgoing telephone line to thereby establish a connection between the call-diverter station and a predetermined remote telephone station. The successive operations of the call-diverter often are conditioned upon the answering of the transferred call at the remote station. That is, the connection of the call-diverter to the outgoing telephone line will be maintained for an indefinite period so long as the remote station is not answered and the incoming caller persists in retaining his connection to the call-diverter station. It has been found that it would be desirable to provide a predetermined time duration during which the remote telephone station must be answered; and if not then answered, the call-diverter should be restored to its initial, quiescent state.
In some call-diverter systems, the connection between the incoming telephone line and the call-diverter itself is deferred until after the transferred call to the remote telephone station has been answered. This insures that a tariff is not unnecessarily imposed upon the incoming caller for the completion of his call to the call-diverter station when the transferred call cannot be completed -- the remote station being "busy" or unattended, or because of other problems attending the telephone switching network. Although such deferred completion to the incoming telephone line is economically favorable, the incoming caller generally is not aware that his call has been received by a call-diverter system and that, for some reason, such call is unable to be successfully transferred. Thus, the incoming caller merely hears the usual ringback signal but does not know why his call is delayed.
One proposed solution has been to connect the incoming line to the call-diverter immediately upon sensing an incoming ringing signal to thereby provide a connection through the call-diverter to the outgoing telephone line. In this manner the caller is not only made aware of the ringback produced in response to his call to the call-diverter system, but he is also enabled to listen to the various supervisory signals accompanying the transfer of his call to the remote telephone station. Hence, he can hear the transmitted dialing signals and the remote station ringback or busy tones, indicating the condition of the remote telephone station. Accordingly, the caller can make the determination of whether the remote station is unattended or is temporarily in use. This information will enable him to formulate his further actions, such as whether and when he should attempt to repeat his call, or whether he should remain coupled to the call-diverter station and permit the continual ringing at the remote station. Unfortunately, such immediate, direct connection between the incoming telephone line and the call-diverter station results in an assessment to the caller for that call. Hence, even though communication with a desired party has not been effected, the calling party, nevertheless, is charged for the "uncompleted" call.
Therefore, it is an object of the present invention to provide an improved telephone call-diverter system that overcomes the aforenoted problems attending prior art systems.
It is another object of the present invention to provide an improved telephone call-diverter system wherein solid-state semiconductor components are employed to perform the various switching and sensing functions.
Yet another object of this invention is to provide an improved telephone call-diverter system wherein the system is returned to an initial, quiescent condition in the event that a call, transferred to a remote station, is not completed within a predetermined interval of time.
A still further object of this invention is to provide an improved telephone call-diverter system wherein a DC connection between an incoming telephone line and the call-diverter system is not completed until the transferred call is answered at the remote station, thereby operating the telephone system tolling apparatus; and wherein a voice frequency channel is also provided between the incoming telephone line and the call-diverter system to thereby enable a caller to perceive the various conditions of the system, regardless of the DC connection.
An additional object of this invention is to provide an improved telephone call-diverter system wherein a selective DC connection between the call-diverter system and an incoming telephone line is shunted by an audio signal transmission connection.
Another object of this invention is to provide an improved telephone call-diverter system wherein the completion of a DC connection between an incoming telephone line and the call-diverter system is inhibited until after the predetermined remote telephone station, to which the incoming call is transferred, is connected to the call-diverter system.
Various other objects and advantages of the present invention will become apparent from the forthcoming detailed description thereof, and the novel features will be particularly pointed out in the appended claims.